To obtain this classification, the first of its kind, ATRA examined publicly available information on 15 criteria, such as the average age of the aircraft used or the homogeneity of the fleet, it said.
The agency explained that to understand airline safety, one needed not only to look at accident figures, but also "technical, human, organisational and external" elements.
"Even though the European Union publishes a 'blacklist' of dangerous airlines, there exists a real difference in safety between the other airline companies," ATRA added.
